Process for treating of cellulose material



T. KLEINERT PROCESS FOR TREATING OF CELLULOSE MATERIAL July 10, 1951 Filed Nov. 14, 1947 Ffg/I Fl'g. 5

INVQNTOR ,3, MMw a/mw Patented July 10, 1951 PROCESS FOR.TREATING OF CELLULOSE MATERIAL Theodor Kleinert, Vienna, Austria, assignor to Lenzinger Zellwolleund-"Papierfabrik' Akti'engesellschaft, Lenzing-Agerzell, Upper Austria Application'November'l l, 1947, Serial No. 786,115 InAustria March 24, 194.7.

(Cl. 260Y-212) 8 Claims. 1.,

The present invention relatesto a process'for the breakdown oficelluloseby'oxidation for the purpose of conversion into cellulose derivatives, more: particularly inthe manufacture of viscose. In this process elementary oxygen or a mixture of gasescontaining oxygenysuch as air, is allowed tor'acton alkali cellulose.

Itiis the object of the present invention to convert alkali cellulose fibers into derivatives thereof by: combinedm'hemica'l and mechanical treatment insuch axmanner that as intense a chemi-calactionof the oxidizing gases onthe fibers as pos sible is effected.

It isaiurther object of' the inventionrto providean: apparatus'which; While simple in design and'inexpensive in manufacturing costs, enables the-'most-efiective-chemical action of the. oxidizing agent'uponthe alkali cellulose under treatment;

With: this purpose in view, the. treatment according to the invention comprises'lbringing alkali. cellulose fibers into a state of fine dispersion in caustic alkali solution and allowing-said dispersedparticles to interact with the oxidizing gas particles-over-wide contact areas. According to a preferred" method thertreatment iscarried out by throwing particles of the suspension up into a gasfilled'space-bymeans ofa pluralityof powerful. boaters. These beatersmay, at the same'time, be so designed as to efifect injuries of thexouter fiber membranes, whereby the oxidizing: gas: can perform more direct action on the cellulose substance.

Other objects and features-of the invention will be'apparent from. the following: description and the'accomp'anying:drawing.

Theprocess, according toth'e invention,,mainly-consists inthesfollowing: A suspension of'alkali cellulose in caustic alkali solution of at least 8% (by weight), preferably 16-24% of sodium hydroxide, is dispersed in'the course of the oxidizing treatment in such a Way that-new portions of the mixture of caustic-solutionand fibers are continually brought into contact with the continuous gaseousphase'of theoxidizing gas, while the contactsurfacesof the liquid and gaseous phases are atleast" temporarily enlarged. It is desirable that the suspension contains-not' more than 23-10% alkali-cellulose fibers, preferably not more than 3-6%. It has been found that the best mechanical treatment. cf'the mixture of caustic. solution and alkali fibers'in presencerof the gas is one which at the same time causes a mechanical damage and injuryof the fibers; By-thusinjuring .the' outer membrane of the fibers, a direct action of the oxidizing-gas on the substanceof the cellulose is enhanced. l

Under these' conditions, the breakdown of'the alkali cellulose suspended in the caustic solution occurs-rapidly and evenly.

There are diiierent ways to obtain the largest possible contact surfaces of the phases as re quired according to the invention. I consider mainly thebea'ting of air or of other oxygen containing gases into the alkali cellulose pulp and the introduction of the alkali cellulose pulp into the space filled with the oxidizing gas-in the form of thin layers or in other fine distribution.

According to one method of practicing the invention, air or the like isbeaten into the alkali cellulose pulp by a large number of rapidly rotating' beaters; these heaters continuallythrow part of the liquid up into the. gas-filled space and thus bring about the intimate contact of the liquid particles with the gas, at'the same time incorporating the finely: dispersed gas into the liquid. In this way, to the action of the gas distributed in the liquid; is added the action of the'gas upon the thin layers of liquid thrown up into the gas, and by such an increasetoftliecon tactsurfaces of'the phases a much greater effect is achieved. lnthis-method itis importanttthat the pulp is treated in a a container which is filled toa considerable extent, preferably- 15 to 20% and more; witlian oxidizing gas; such as air. Especially byusing installations having a gas-filled space comprising 30 to of the total volume, I obtain a rapid and even oxidizing efiect by adding to the beating of the air into. the liquid the catapulti'ng' of droplets of the liquid into'tl'ie' gas space. Since'it'is essential, incarrying out theinvention; to continually bring into contact with the gas'new portionsofthe't liquid; a device is provided" for" the. heating of air into the liquid; which. comprises a'cnumber of beaters distributed over'a: portion of .the path' of thei-liqui'd thereby causing'a" movement of constantly new particles of the liquid.

The heaters, which are: alternately" moved through the liquid and the gaseous phases, may have difierent designs; for instance they may be inthe shapeof rods; plates, disks, more particularlyperforated platesor disks, or the like, which; onthe one hand'intro'duce liquid into the gas filled space, and 'Onthe other hand gas-into the liquid mass. By: making the single-heaters smalllin size'nar row beatershavinghigh moment-of inertia-and, byincreasing the numberof heaters, itis; possible to promote the distribution of the phases without increasing the input of work. In order to achieve a more intensive mechanical working of the fibers, it is advantageous to provide the heaters with Sharp edges. A particular embodiment of the device according to the invention comprises an assembly of beaters, in which all or some of the beaters, owing to the special shape thereof, are adapted simultaneously to advance the alkali cellulose pulp through the apparatus obliquely to the direction of their movement.

According to another embodiment I use, instead of heaters, perforated plates or disks which are mounted upon the shafts and are of a diameter that corresponds to the beating space. Sharp edges on the perforations have a favorable effect on the mechanical processing of the fibers. If the perforations are set at an angle with respect to the axis of rotation, the material is simultaneously fed in the direction of the axis of rotation.

According to one particular form of the process according to the invention, the alkali cellulose pulp under treatment is continuously moved with the oxidizing gas, either in the same direction or in counter-current thereto. In this case, too, the liquid mass may be moved through theap paratus, transversely to the direction of the beating, by means of the boaters themselves, or the movement may at least be promoted by them.

According to yet another method, the desired oxidizing action of the gas upon the pulp, which has been finely dispersed by throwing action, can be brought about by devices similar to disk washers. Or the particles of the liquid may be treated with the gas in excess in such a manner that the liquid is divided into jets which are passed into the gas-filled space, for instance by pressing the pulp through sieves or the like.

These various methods may be combined, if so desired, for example by beating air into a suspension of alkali cellulose in caustic soda solution and thereafter pressing the three-phase system through sieves in order to obtain a homogenized mixture.

The process according to the invention may be combined with an oxidizing treatment of the alkali cellulose pulp, by allowing oxygen in finely dispersed state, or a gas mixture containing oxygen in such state, to act on the mixture of fibers and caustic solution. In carrying out this process, the finely dispersed oxidizing gas is introduced, during or after the alkali cellulose pulp is distributed, into that part of the pulp which forms I a continuous liquid-solid phase.

The process according to the invention is preferably carried out in such a way that the liquid contains percent or more (by volume) of gas mechanically distributed therein during the mechanical treatment above mentioned.

After termination of the treatment according to the invention, it is desirable to allow the pulp, which contains the gas, to stand for several hours in order to make possible an additional reaction between the alkali cellulose and the incorporated air. If necessary, the treatment of the pulp with oxidizing gas may be repeated.

The accompanying drawing illustrates, by way of example, several embodiments of apparatus adapted for carrying out the process according to the invention. In this drawing Fig. 1 shows, in longitudinal section, an embodiment of an apparatus with a cylindrical housing; Fig. 2, likewise in longitudinal section,

another form of apparatus having a conical housing, with beating device and sieve for distributing the liquid; Figs. 3 and 4 illustrate a preforated plate for carrying out the invention, Fig. 3 being a section along line IIIIII of Fig. 4; and Fig. 5 shows a differently-shaped element in the form of a helical disk.

Referring now to the above mentioned drawing, numeral l in Fig. 1 designates a cylindrical housing in horizontal position, through which extends a shaft 2. The shaft is mounted in end bearings 3 and 4'and, if required in view of the length of the housing, in one or more intermediate bearings. The bearings are supported on the housing and fastened thereto by means of perforated sheets, lands, or the like. Mounted on shaft 2, at a certain distance from each other, are disk-shaped elements 5, which extend close to the cylindrical wall of the housing. Between elements 5, conveyer elements 8 are mounted, which are of smaller diameter. The housing is partly filed with pulp a through which the lower portions of elements 5 and 8 move. Above the pulp a is the space b filled with oxidizing gas, through which the upper parts of elements5 and 8 rotate. A drive means, not shown in the drawing, causes the shaft and the elements mounted thereon to rotate rapidly in the direction of the arrow 12.

In the illustrated example, elements 5 are disk shaped, preferably as shown in Figs. 3 and 4. In this embodiment, each disk has a certain number of holes 6, which are distributed as evenlyas possible, and which, with reference to the sense of rotation of said disk (arrow p), are obliquely positioned in such a manner, that the sharp edges 6 formed thereby will grip the pulp at the'bottom part of the rotating disk and cause a deviation of the pulp in the direction of arrow q, thus creating a current of the pulp in that direction. Moreover, the sharp edges 6 will effeet a mechanical processing of the fiber material contained in the pulp. By holes 6, too, pulp is taken up and thrown into the gas space I), and conversely gas or air is forced into the pulp.

Elements 8 consist, in the embodiment here shown, of helical sheets of low pitch, which during rotation of the shaft in the direction of arrow p move part of the pulp in a direction opposed to arrow q. The helical sheets 8 may also be provided with holes or cut-out portions, in order to perform a beating action simultaneously with the feeding action, similar to elements 5. On the other hand, beaters 5 may also consist of helical sheets of low pitch, as shown for example in Fig. 5. In this case the pitch of the helix effects the movement of the fiber material, acting as a conveyor, so that the holes, cut openings, protruding and cutting edges, etc., only serve as means for the mechanical treatmentof the fibers in the pulp, as well as for the introduction of pulp into the gas and vice versa, and they should be designed so as to serve these purposes to perfection.

In the example as shown in Fig. 2, the rapidly rotating shaft 2 extends through a housing II which is conically tapered in the direction of flow p of the pulp. The bearings for the shaft are again designated by 3 and 4, and the working elements on the shaft by 5 and 8. They are similar to the elements illustrated in Figs. 1 and 3 to 5, respectively. At the discharge end of housing H, a device is attached, which comprises a thrust wheel [6 mounted on a rapidly rotating shaft I5 and enclosed by an annular sieve ll. An annular gas space It! is arranged around sieve H. In this apparatus, the liquid is taken up by wheel 16 and pressed through sieve ll, whereby it is divided into fine jets and, in this form, introduced into the gas space l8. It is obvious that the apparatus comprising elements IE to I8 may be used by itself, or in combination with other suitable devices, for the mechanical treatment of alkali cellulose pulps with oxidizing gas.

In the illustrated embodiments the elements 5 are in the form of disks; however, they may also consist of cross-armed beaters having arms of various cross-section, such as square, triangular, etc., and having preferably sharp or cutting edges. If desired, said arms may be joined at their outer rims by a hoop-shaped member of solid or perforated material, for instance a strip of sieve. Housings l and l l, respectively, and the shafts mounted therein, may also be positioned at an angle.

I claim:

1. A process for breaking down cellulose material comprising preparing a suspension of alkali cellulose in caustic soda solution of at least 8 percent by weight of sodium hydroxide and not more than 10 percent by weight of alkali cellulose fibers, continuously projecting particles of said suspension into a gaseous oxidizing medium and simultaneously therewith driving a portion of the said oxidizing medium into the said suspension.

2. A process for breaking down cellulose material comprising preparing a suspension of alkali cellulose in caustic soda solution, said suspension having from 16 to 24 percent by weight of sodium hydroxide and from 3 to 6 percent by weight of alkali cellulose fibers, and projecting particles of said suspension into a body of air.

3. A process for breaking down cellulose material comprising the steps of continuously moving a suspension of alkali cellulose in caustic solution through a container in contact with a gaseous oxidizing medium, said suspension having from 16 to 24 percent by weight of sodium hydroxide and from 3 to 6 percent by weight of alkali cellulose fibers, projecting particles of said suspension into the gaseous oxidizing medium during the movement of the said suspension and simultaneously therewith drivinga portion of the said gaseous oxidizing medium into the said suspension.

4. A process for breaking down cellulose material which comprises continuously moving a suspension of alkali cellulose in caustic soda solution in contact with air, said suspension having from 16 to 24 percent by weight of sodium hydroxide and from 3 to 6 percent by weight of alkali cellulose fibers, projecting particles of said suspension into the air during the movement of the said suspension and simultaneously therewith driving a portion of the said gaseous oxidizing medium into the said suspension.

5. A process for breaking down cellulose material which comprises the steps of continuously moving a suspension of alkali cellulose in caustic soda solution in contact with a continuous stream of air, said suspension having from 6 to 24 percent by weight of sodium hydroxide and from 3 to 6 percent by weight of alkali cellulose fibers, projecting particles of said suspension into the air during the movement of the said suspension and simultaneously therewith drivinga portion of the said gaseous oxidizing medium into the said suspension.

6. A process for breaking down cellulose material which comprises the steps of passing a stream of a suspension of cellulose particles in caustic alkali solution through a container in contact with a gaseous oxidizing medium at atmospheric pressure, mechanically injuring suspended cellulose particles and projecting the injured particles into the said medium, and simultaneously therewith driving a portion of the said oxidizing medium into the said suspension.

7. A process as claimed in claim 6 in which the suspension of cellulose particles passed into contact with said oxidizing medium comprises about 3 to 6 percent by weight of cellulose particles and from 16-24 /percent by weight of sodium hydroxide.

8. A process as claimed in claim 6 in which the oxidizing medium is present in amounts of at 35 least 20 percent by volume of the contacting oxidizing medium and suspension.

THEODOR KLEINERT.

REFERENCES CITED UNITED STATESPATENTS Number Name Date 745 1,279,328 Glover et al Sept. 17, 1918 1,632,340 Kipper June 14, 1927 1,834,693 Frischer Dec. 1, 1931 1,859,579 Bidaud May 24, 1932 1,860,432 Richter May 31, 1932 1,955,092 Richter Apr. 17, 1934 2,139,302 Brooys Dec. 6, 1938 2,482,042 Van Delden Sept. 13, 1949 FOREIGN PATENTS Number Country Date 14,675 Great Britain of 1914 OTHER REFERENCES Ott, Cellulose and Cellulose Derivatives," 1943, pages 740-744. 

1. A PROCESS FOR BREAKING DOWN CELLULOSE MATERIAL COMPRISING PREPARING A SUPENSION OF ALKALI CELLULOSE IN CAUSTIC SODA SOLUTION OF AT LEAST 8 PERCENT BY WEIGHT OF SODIUM HYDROXIDE AND NOT MORE THAN 10 PERCENT BY WEIGHT OF ALKALI CELLULOSE FIBERS, CONTINUOUSLY PROJECTING PARTICLES OF SAID SUSPENSION INTO A GASEOUS OXIDIZING MEDIUM AND SIMULTANEOUSLY THEREWITH DRIVING A PORTION OF THE SAID OXIDIZING MEDIUM INTO THE SAID SUSPENSION. 